Spinning Black Hole Observed for the First Time

Artist's impression of a spinning supermassive black hole with a surrounding accretion disk and relativistic jets. Note the compact, X-ray bright region at the base of the jet.

NASA/JPL-Caltech

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ProbingaSpinningBlackHole:Pictures

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Artist's impression of a spinning supermassive black hole with a surrounding accretion disk and relativistic jets.

NASA/JPL-Caltech

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How to measure the spin of a black hole: This chart illustrates the basic model for determining the spin rates of black holes. The
three artist's concepts represent the different types of spin: retrograde rotation, where
the disk of matter falling onto the hole, called an accretion disk, moves in the opposite
direction of the black hole; no spin; and prograde rotation, where the disk spins in the
same direction as the black hole.

NASA/JPL-Caltech

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Two models of black hole spin: Scientists measure the spin rates of supermassive black holes by spreading the X-ray
light into different colors. The light comes from accretion disks that swirl around black
holes, as shown in both of the artist's concepts. They use X-ray space telescopes to
study these colors, and, in particular, look for a "fingerprint" of iron -- the peak shown
in both graphs, or spectra -- to see how sharp it is. Prior to observations with NASA's
Spectroscopic Telescope Array, or NuSTAR, and the European Space Agency's XMM-
Newton telescope, there were two competing models to explain why this peak might not
appear to be sharp.
The "rotation" model shown at top held that the iron feature was being spread out by
distorting effects caused by the immense gravity of the black hole. If this model were
correct, then the amount of distortion seen in the iron feature should reveal the spin rate
of the black hole.
The alternate model held that obscuring clouds lying near the black hole were making
the iron line appear artificially distorted. If this model were correct, the data could not be
used to measure black hole spin.

NASA/JPL-Caltech

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This chart depicts the electromagnetic spectrum, highlighting the X-ray portion. NASA's
Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency's
XMM-Newton telescope complement each other by seeing different colors of X-ray light.
XMM-Newton sees X-rays with energies between 0.1 and 10 kiloelectron volts (keV),
the "red" part of the spectrum, while NuSTAR sees the highest-energy, or "bluest," X-
ray light, with energies between 3 and 70 keV.

NASA/JPL-Caltech

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This image taken by the ultraviolet-light monitoring camera on the European Space
Agency's (ESA's) XMM-Newton telescope shows the beautiful spiral arms of the galaxy
NGC1365. Copious high-energy X-ray emission is emitted by the host galaxy, and by
many background sources. The large regions observed by previous satellites contain so
much of this background emission that the radiation from the central black hole is mixed
and diluted into it. NuSTAR, NASA's newest X-ray observatory, is able to isolate the
emission from the black hole, allowing a far more precise analysis of its properties.

ESA

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What XMM-Newton saw: The solid lines show two theoretical models that explain the low-energy X-ray emission
seen from the galaxy NGC 1365 by the European Space Agency's XMM-Newton. The
red line explains the emission using a model where clouds of dust and gas partially block
the X-ray light, and the green line represents a model in which the emission is reflected
off the inner edge of the accretion disk, very close to the black hole. The blue circles
show the measurements from XMM-Newton, which are explained equally well by both
models.

NASA/JPL-Caltech/ESA/CfA/INAF

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Two X-ray observatories are better than one: NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, has helped to show, for
the first time, that the spin rates of black holes can be measured conclusively. It did this,
together with the European Space Agency's XMM-Newton, by ruling out the possibility
that obscuring clouds were partially blocking X-ray right coming from black holes.
The solid lines show two theoretical models that explain low-energy X-ray emission seen
previously from the spiral galaxy NGC 1365 by XMM-Newton. The red line explains the
emission using a model where clouds of dust and gas partially block the X-ray light, and
the green line represents a model in which the emission is reflected off the inner edge of
the accretion disk, very close to the black hole.
The blue circles show the latest measurements from XMM-Newton, and the yellow
circles show the data from NuSTAR. While both models fit the XMM-Newton data
equally well, only the disk reflection model fits the NuSTAR data.

Astronomers have conclusively measured the spin of a black hole for the first time by detecting the mind-bending relativistic effects that warp space-time at the very edge of its event horizon -- the point of no return, beyond which even light cannot escape.

By monitoring X-ray emissions from iron ions (iron atoms with some electrons missing) trapped in the black hole’s accretion disk, the rapidly-rotating inner edge of the disk of hot material has provided direct information about how fast the black hole is spinning.

And by doing this, a long-standing controversy surrounding black hole studies has been laid to rest.

The spinning supermassive black hole lives in the heart of the nucleus of NGC 1365, a nearby galaxy some 56 million light-years away.

X-Ray Fireworks

Accretion disks consist of any material that has drifted too close to the gravitational dominance of a black hole. Gas, dust, even stars succumb to the force inside an active galactic nucleus (AGN). Some material will feed the black hole, whereas a surplus of matter is ejected from the black hole’s poles, blasting into space as jets of material traveling close to the speed of light, generating an intense cosmic fireworks display.

AGNs can be dazzling, shining bright in X-ray radiation -- an indication that the supermassive black hole lurking inside is feeding.

“The accretion disk isn’t hot enough to generate X-rays itself, these X-rays generated in the jet shine down on the disk and reflect off of it, exciting the iron,” Fiona Harrison, professor of physics and astronomy at the California Institute of Technology, Pasadena, Calif., and principal investigator of the NuSTAR mission, told Discovery News. “That’s what enables us to see the accretion disk -- we’re seeing reflected X-rays off the disk.”

“We selected (NGC 1365) because it is bright in X-rays, and previous observations with less powerful satellites suggested that this could be a good candidate for such a study,” said astronomer Guido Risaliti, of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., and the Italian National Institute for Astrophysics, and lead author of research published today (Feb. 27) in the journal Nature.

The environment near the black hole’s event horizon is extreme; the fabric of space-time itself is being warped by the spin of the black hole, dragging the inner edge of the accretion disk with it. As the disk of material rapidly rotates -- like the vortex of a water funnel down a plughole -- it is still emitting X-rays.

The emission from this component of the accretion disk should therefore be stretched, or redshifted, providing astronomers with a means of quantifying how fast the black hole is spinning.

“We’re actually using the rotation of the disk to measure the spin of the black hole,” Harrison added.